Project Summary/Abstract Hearing and listening are critical to how adolescents communicate, learn new information, and engage with technology and culture; however, performance on auditory perceptual tasks takes a long time to become mature. Because few studies of auditory perception have centered on typically-developing adolescents, little is known about the mechanisms underlying this immaturity. The lack of knowledge of the processes underlying the prolonged maturation of hearing and listening abilities in typical listeners can lead to difficulties in the diagnosis of auditory processing disorders and other communication disorders, thus affecting public health. The long- term goal of this project is to elucidate the mechanisms underlying the development of auditory perception during adolescence. The present objective is to evaluate the extent to which auditory stimulus encoding and various cognitive processes contribute to immature auditory perception during adolescence. The central hypothesis is that immature performance on auditory and speech perception tasks during adolescence can be attributed to both maturational changes in temporal encoding and to developmental improvements in the specific cognitive processes required by each task. This hypothesis will be tested by pursuing two specific aims: (1) Evaluate the contribution of auditory temporal processing and cognitive functions to immature naïve performance on basic auditory tasks during adolescence. (2) Evaluate the contribution of auditory temporal processing and cognitive functions to naïve performance on speech perception tasks during adolescence. These aims will be addressed using a combination of perceptual testing, pupillometry and blink-rate to index cognitive processes engaged during active listening, auditory evoked potentials to index temporal and spectral encoding during unattended stimulus presentations, and standardized neuropsychological and language tests to evaluate processes with known maturational courses. This project will yield experimental protocols that will be applicable for the development of diagnostic tests regarding auditory processing in adolescents and young adults. It also could inform future therapies that aim to support or improve the processes underlying auditory perception in adolescents and young adults with communication disorders.